Current production automobiles comprise a body formed on a plurality of longitudinal structural steel frame members. Prototype and experimental vehicles with composite frame members have been proposed. In a front engine automobile of this type, a full frontal impact has three principle paths for impact force transmission to and through the vehicle structure. These are outer paths comprising upper and lower longitudinal frame members, and a central path comprising the engine, transmission and, possibly, the engine cradle.
In a full frontal impact at sufficiently high speeds, all three load paths are functional to absorb and dissipate the vehicle's energy as it rapidly decelerates. Testing has shown that the outer load paths together dissipate 40%-70% of the vehicle's energy, while the central path dissipates the remainder. The side longitudinal rails are designed to dissipate energy by deforming at force levels that will provide passenger compartment decelerations consistent with occupant safety requirements.
While a full frontal impact engages the entire front end and all three of an automobile's load paths, in an offset frontal impact, there is only partial overlapping of the fronts of the colliding vehicles. Two techniques have been published which address offset frontal impacts in current production vehicles having steel structural members.
The first technique links the crush responses of the two side load paths through the use of robust cross-car members, such as tie-bars, radiator support brackets, and the engine cradle, in combination with the use of more rigid joints between the longitudinal and cross-car members. The second technique reinforces the passenger compartment to help maintain its integrity.
For both metal structures and proposed composite structures, these techniques have the shortcoming of requiring added structure, which increases vehicle mass and decreases effective crush space. In composite structures, these techniques make crush control problematic, since they make it difficult to initiate and maintain the progressive rail crush needed for proper response.
Thus, there is a need for a crush control technique or method of assuring initiation and maintenance of progressive crush for composite structures at appropriate force levels for both full frontal and offset frontal vehicle impacts.
There is also a need for apparatus that carries out such a method by functioning to initiate and maintain progressive crush for composite structures at appropriate force levels for both full frontal and offset frontal vehicle impacts.